1. Field of the Invention
The present invention relates to an antenna device with a sub-antenna device configured to be electrically connected to or separated from a sliding up-type mobile phone, sliding up or down along the mobile phone.
2. Description of the Related Art
The term “portable communication device” typically refers to a device that allows a user to wirelessly communicate with an other party, while being convenient to carry. Portable communication devices include HHPs (Hand Held Phones), CT-2 (Cordless Telephones-2), cellular phones, digital phones, PCS (Personal Communications Service) phones, and PDAs (Personal Digital Assistants). The devices are classified into a plurality of types according to their appearance. For example, mobile phones are classified into a bar type, a flip type, a folder type, a sliding type, and a sliding-up type. The mobile phones each are provided with an antenna device, a data input/output device, and a data transmitter and receiver. An LCD (Liquid Crystal Display) is usually adopted as a visual data output device.
A keypad is typically provided for data input, basically as an array of keys. These keys include a Send (SND) key, a Cancel key, a Clear (CLR) key, an End key, a Power (PWR) key, alphanumerical keys, and other function keys.
A recent soaring increase in the number of mobile users indicates that mobile phones are becoming a necessity. Beyond the original function of making phone calls, the mobile phones can now be additionally used to listen to the radio, listen to MP3 music, and view moving pictures, and used as a remote control device.
Also, mobile phones have been developed to have a camera and support high-speed data communication. This implies that many devices are mounted into the mobile phone to satisfy various user demands. As these devices are used, they occupy various areas within the phone, and the area for installing a built-in antenna is reduced.
To allow the mobile phone to perform the above-described voice and other wireless functions, an antenna device is located at a proper position of a mobile phone to transmit and receive signals. The antenna device typically takes the form of a whip antenna or a helical antenna.
The helical antenna is more common in that it boasts of a decreased antenna height in an installed state. Unlike an extendable rod antenna, the helical antenna is detachably fixed to an upper end of a main body, having a portion extended upward in the mobile phone. The protruded configuration of the helical antenna limits the design options of mobile phones that use a helical antenna.
To overcome the drawback of the helical antenna, a built-in antenna device has become widespread in mobile phones.
Referring to FIGS. 1, 2 and 3, a sliding up-type mobile phone 10 includes a body housing 20, a sliding housing 30 disposed above the body housing 20, for sliding up/down to recede from/approach the body housing 20, and a sliding module 40 for connecting the sliding housing 30 to the body housing 20 in the manner that allows the sliding housing 30 to slide up/down. The body housing 20 has a display 21, an array of keys 22, and a microphone 23. The sliding housing 30 is provided with a speaker 31 and a main antenna device 32.
The conventional antenna device in the sliding up-type mobile phone is built on an inner surface of the sliding housing, to slide lengthwise. This configuration changes the impedance of the antenna device as the sliding housing slides up or down. Because the radiation performance of the mobile phone depends on impedance matching, an inappropriately matched impedance results in insufficient antenna orientation and gain, and makes it difficult to achieve maximum radiation performance.